It is often necessary to modify the sample rate of a digital audio signal or to change the number of samples that represent a particular time segment of an audio signal in a file or digital store. Such modifications are used to synchronise the sample rates of independently-sourced digital signals, or to modify the size of a file or data set. A temporary increase or decrease in the sampling frequency can also be used as a means of delaying or advancing the timing of audio information.
Where there are no limitations on processing time or complexity, interpolation of new samples having the required sampling frequency and phase by taking weighted sums of existing samples is often the preferred method. However, a known alternative method, which has the advantage of not introducing significant delay in real-time processing applications, is the deletion or repetition of samples at points chosen to minimise the audibility of the deletion or repetition. An effective method for identifying such points is thus an important feature of audio sample rate converters operating by sample deletion and repetition.